There are known fine particle measurement devices that form laminar flows containing fine particles in flow passages formed in flow cells, microchips, or the like and radiate light to the fine particles in the laminar flows to detect fluorescence and scattered light produced from the fine particles. For example, flow cytometers can measure and analyze optical characteristics of fine particles such as cells, beads, and the like based on the intensity or spectrum of detected fluorescence or scattered light.
In fine particle measurement devices, laminar flows are formed in substantially the middles of flow passages so that fine particles are circulated. Examples of the mechanism include a method of forming a sheath flow and focusing a liquid containing fine particles on the middle of a flow passage, an acoustic focusing method of aggregating fine particles on the middle of a flow passage with the energy of a sound, and a combination method thereof. However, when dust or bubbles are mixed in a flow passage, disturbance occurs in a laminar flow, a variation in the circulation positions of individual fine particles in the flow passage occurs, accurate measurement is not performed, and thus a problem occurs in reliability of data in some cases. Further, noise occurring from the dust or bubbles mixed in the flow passage deteriorates precision of data in some cases.
In relation to an embodiment of the present technology, technologies for suppressing a measurement error caused due to the variation in the circulation positions of fine particles in a flow passage are disclosed in Patent Literature 1 and Patent Literature 2. In a fluid particle analysis device disclosed in Patent Literature 1, detected light (scattered light) extracted from front scattered light, side scattered light, or rear scattered light via an optical divider is detected by a 4-split photodiode, an area CCD, and the like. Then, a position deviation from the detected position between the center of excitation light and the center of a sheath flow is detected and a position of the flow cell is adjusted so that the position deviation is within a predetermined range. Further, Patent Literature 2 discloses a technology for detecting position information regarding fine particles using a change in a deflection angle occurring in scattered light produced from the fine particles and adjusting the position of a flow cell or the focal position of the excitation light.